The power supply device (200) comprises a vibrating probe (122) having conductivity, a gripping member (134) opening and closing with respect to the probe (122), electrodes (136) provided on the gripping member (134) (200) for supplying high frequency power between a probe (122) and an electrode (136) of a treatment instrument (100) including a probe (100). The power supply apparatus (200) includes a resistance acquisition circuit (214) for repeatedly acquiring a resistance value relating to electric resistance between the probe (122) and the electrode (136), a resistance acquisition circuit A condition judging circuit (216) for acquiring the number of times the resistance value satisfies a predetermined condition while electric power is being supplied between the probe (122) and the electrode (136), and a probe judgment circuit And a determination circuit (218) for determining whether the electrode (136) is electrically short-circuited or not.電源装置(200)は、導電性を備えている振動するプローブ(122)と、プローブ(122)に対して開閉する把持部材(134)と、把持部材(134)に設けられた電極(136)とを備えた処置具(100)の、プローブ(122)と電極(136)との間に高周波電力を供給する電源装置(200)である。電源装置(200)は、プローブ(122)と電極(136)との間の電気抵抗に係る抵抗値を繰り返し取得する抵抗取得回路(214)と、プローブ(122)が振動しており、かつ、プローブ(122)と電極(136)との間に電力が供給されている間に、抵抗値が所定の条件を満たす回数を取得する条件判断回路(216)と、回数に基づいて、プローブ(122)と電極(136)とが電気的に短絡しているか否かを判定する判定回路(218)とを備える。
